Mathematical analysis of bioelectrochemical systems

在英国，每年都要花费大量的能源和数十亿英镑来处理工业/家庭/城市废水。然而，这种通常含有大量有机化合物的废水实际上可以用作生物电化学系统（BESs）设备中的宝贵资源。BES与其他电化学电池（如电池）一样，由阳极、阴极和分离膜（可选）组成，但不同之处在于如何催化电化学反应。在BES中，至少一个或两个电极反应在微生物的帮助下被催化。通过将活体生物系统与电化学相结合，BES使利用废水中的化学能发电（微生物燃料电池，mfc）、制氢（微生物电解电池，MECs）或增值化学品（微生物电合成，MES）成为可能。在不同的BESs中，一个微生物电合成（MES）系统，其中两个电极都是生物催化的，可以将废水（在生物阳极输入）和二氧化碳（在生物阴极输入）转化为有用的多碳化合物，这些化合物是商品化学品和运输燃料的前体。因此，这种MES系统在废水处理以及二氧化碳捕获和利用方面具有特别的意义。然而，MES中的电化学反应是非自发的，需要外部能量。可再生能源（太阳能、风能）可用于提供所需的电力。因此，MES还提供了一种新颖的方法，将可再生电能存储在有机化合物的化学键中，这种化学键可以更容易地存储和运输。MES系统的性能取决于许多生物、物理化学和电化学参数。在2009-2010年的第一次实验演示之后，进行了各种研究，以调查操作参数对MES性能的影响。这些研究有助于提高产品收率，但进一步提高性能需要对控制过程的机制有更深入的了解。过去对MES的研究主要集中在实验研究上，而数学建模一直被忽视。数学模型的发展对未来MES系统的优化和扩展至关重要。目前，还没有可用的数学模型来预测MES过程的整体性能。在这个项目中，我建议开发全面的数学模型，不仅可以提供对MES管理机制的见解，还可以提供MES系统如何影响环境的见解。这样的数值模型将补充实验，并有助于以更低的成本和时间将这项技术推向商业化。开发高效的MES系统，使用低品位的基质，如废水和废二氧化碳进行化学生产，为可持续生物生产和废水处理提供了一个新的技术平台。这样的系统可以以一种综合的方式帮助解决环境和能源挑战。通过消耗二氧化碳来生产生物化学品也将减少目前化学工业对化石燃料碳源的依赖，并有助于英国实现其气候目标。因此，除了经济和生态效益外，MES研究也具有重要的社会意义。虽然拟议的研究主要集中在MES系统上，但从这些模型中获得的见解也将适用于类似的生物电化学系统，如微生物燃料电池和微生物电解电池。因此，研究成果将直接有助于推广这种可持续的技术，用于各种化学品的生物生产（MES， MEC）以及从废水中产生可再生电力（MFC）。

Significant amount of energy and billions of pounds are spent every year in UK to treat the industrial/domestic/municipal wastewater. However, this wastewater which typically contains a lot of organic compounds can actually be used as a valuable resource in devices known as bioelectrochemical systems (BESs). BES are like any other electrochemical cell (e.g. battery) and consist of an anode, cathode and a separating membrane (optional), but the difference lies in how the electrochemical reaction is catalysed. In BES, at least one or both of the electrode reactions are catalysed with the help of microorganisms. By combining living biological systems with electrochemistry, BES makes it possible to utilize the chemical energy from wastewater and generate electricity (microbial fuel cells, MFCs), hydrogen (microbial electrolysis cells, MECs) or value-added chemicals (microbial electrosynthesis, MES). Among different BESs, a microbial electrosynthesis (MES) system in which both electrodes are biocatalysed, makes it possible to convert wastewater (fed at the bio-anode) and waste CO2 (fed at the bio-cathode) into useful multi-carbon compounds that are precursors to commodity chemicals and transportation fuels. Such MES systems are thus of particular interest in the context of both wastewater treatment as well as CO2 capture and utilization. The electrochemical reaction in MES is however non-spontaneous and requires external energy. Renewable energy sources (solar, wind) can be used to supply the required power. Thus MES also offers a novel way to store the renewable electrical energy in the chemical bonds of organic compounds that can be stored and transported more easily. MES system performance depends on a number of biological, physical-chemical and electrochemical parameters. Following the first experimental demonstration in 2009-2010, a variety of studies have been conducted to investigate the effect of operational parameters on MES performance. These investigations have helped in improving the product yields however further improvements in performance require a deeper understanding of the mechanisms governing the process.Past research on MES has extensively focused on experimental studies, while mathematical modelling has remain neglected. The development of mathematical models will be critical to the optimization and scaling of MES systems in future. At present, there are no mathematical models available to predict the overall performance of the MES process. In this project I propose to develop comprehensive mathematical models that can not only provide insight on the governing mechanisms of MES but also on how MES systems will affect the environment. Such numerical models will compliment experiments and help to develop this technology towards commercialisation at a reduced cost and time. Development of efficient MES systems that use low-grade substrates such as wastewater and waste CO2 for chemical production provide a new technology platform for sustainable bioproduction and wastewater treatment. Such systems can help tackle environment and energy challenges in an integrated approach. Bioproduction of chemicals by consuming CO2 will also reduce the dependency on fossil fuel based carbon sources currently used in chemical industries and can assist the UK in achieving its climate targets. Thus in addition to the economic and ecological benefits, research on MES is also of major societal importance. Though the proposed research is focused on MES systems, the insight obtained from these models will also be applicable for analogous bioelectrochemical systems such as microbial fuel cells and microbial electrolysis cells. Thus the research outcomes will contribute directly towards popularizing such sustainable technologies for bioproduction of wide range of chemicals (MES, MEC) as well as generation of renewable electricity (MFC) from wastewater.